Models for Guiding Management of Prairie Bird Habitat in Northwestern North Dakota

Abstract

With grassland bird populations in the Great Plains exhibiting steep declines, grassland managers require information on bird habitat needs to optimally manage lands dedicated to wildlife. During 1993–1994, we measured bird occurrence and corresponding vegetation attributes on mixed-grass prairie in northwestern North Dakota. Three hundred and ten point-count locations over a wide range of successional stages were sampled. Ten grassland passerine species occurred commonly (i.e., at >10% of point count locations), including two species endemic to the northern Great Plains [Baird's sparrow (Ammodramus bairdii) and Sprague's pipit (Anthus spragueii)], and several species of management concern [bobolink (Dolichonyx oryzivorus), grasshopper sparrow (Ammodramus savannarum), clay-colored sparrow (Spizella pallida)]. Some species were ubiquitous and had generalized habitat associations [e.g., savannah sparrow (Passerculus sandwichensis)]. Others exhibited more finely tuned, closely overlapping use of relatively short, sparse to moderately dense, grass- and forb-dominated habitat. We used logistic regression models to predict bird species' occurrence based on nine vegetation variables. Previously undefined limits of vegetation height and density were identified for Baird's sparrow and Sprague's pipit, and of shrub cover for Baird's sparrow. Our findings underscore the need for a mosaic of successional types to maximize diversity of prairie bird species. Managers may reduce confusion created by generic treatment prescriptions for grasslands by focusing on absolute rather than relative measures of vegetation, and by integrating standard data from multiple bird habitat studies across regions.